1. The field of art to which the invention relates comprises the art of measuring and testing as related to fluid pressure gauges.
2. Pressure gauges enjoy very extensive commercial and industrial use and are consequently regarded as high production items. Because of such wide use, they are supplied by a plurality of manufacturers and sold in very price conscious competition. Each manufacturer instinctively strives to reduce product costs by improvements, however marginal, which reduce labor and/or materials that can contribute to cost savings in the end product. Commonly affording pressure sensitivity in the pressure gauge is a Bourdon tube of a pressure-tight construction having a free end displaceably movable in response to pressure changes supplied at its inlet. To translate tube movement into values of pressure a pointer is supported on its free end which then moves with the tube relative to a calibrated dial plate. For ensuring readout accuracy, provision is usually made either during or after assembly for locating the pointer at the zero position of the dial.
In a conventional construction, the inlet end of the Bourdon tube is secured to the casing and the dial plate is rotatably positioned to effect the zero adjustment. This arrangement is most suitable where ultimate mounting of the gauge affords flexibility in orientation on the equipment for convenient viewing. In instances in which such flexibility is lacking, i.e., where the gauge casing is somehow keyed to the equipment, it is necessary to similarly key the dial plate thereby precluding its rotation for the purpose of zero adjustment. Under those circumstances, it is common to rotate the coil/pointer in effecting the zero calibration. In manufacturing low cost high volume production of the latter type for the fire extinguisher market, the required time and labor to effect zero adjustment has been regarded as disproportionate to the overall value of the finished product. Despite recognition of the problem, a ready solution has not heretofore been known.